Traumatic cardiac arrest (TCA) is a rare event in the pre-hospital setting, with only 0.3% of 227 994 submissions to Trauma Audit and Research Network (TARN) (Barnard et al, 2017a), estimated at 4 per 100 000 of the population annually (Irfan et al, 2017). Outcome following TCA has been widely debated over many years, and the problem is exacerbated by a wide range of outcome measures being quoted as survival, such as return of spontaneous circulation (ROSC) on scene, ROSC at hospital, and neurological outcome at discharge.
A 2016 review of TARN data by Barnard et al (2017a) reported 30-day survival following pre-hospital TCA as 7.5%. Konesky and Guo (2017) retrospectively analysed outcome in 124 patients who suffered TCA. They found 7.3% survival with complete neurological recovery. As a comparison, Irfan et al (2017) report overall survival as 2.4% in 410 patients who suffered TCA. A systematic review by Zwingmann et al (2012) reported overall survival at 7.2%, with varying degrees of neurological outcome. It is important to note that, in England, the introduction of the Major Trauma Networks has significantly changed the way major trauma patients are managed, and this may have an impact on mortality.
HOT approach
Treatment and management is increasingly being directed at the rapid identification and reversal of potential causes. Reversing hypovolaemia, oxygenation and tension pneumothorax (HOT) as a priority is an increasingly accepted guideline (The HOT Approach) (Lockey et al, 2013).
This is based on the theory that treating these reversible causes in a rapid manner gives the patient the best chance of survival having suffered a TCA. The current article discusses application of HOT principles to paramedic practice.
Along with these recommendations is the de-emphasis on the role of chest compressions while reversible causes are addressed. The reason for this is two-fold. Firstly, chest compressions may take up one of the vital and usually under-resourced members of staff attending the incident, and they will therefore be unable to address the reversible causes identified in the HOT approach. Secondly, it is argued that chest compressions are futile if the heart is empty, or is being obstructed from beating (hypovolaemia/tension pneumothorax/cardiac tamponade) (Watts et al, 2017).
Impact of social media
Social media is increasingly used to educate and promote discussion on best practice in medicine (Grajasles et al, 2014). However, issues such as governance and ethics are complex and remain unanswered. There have been a number of discussions, posts and polls on social media showing that many clinicians don't believe there is a role for chest compressions in TCA. This de-emphasis has possibly expanded beyond what can be supported by the current evidence base.
Causes of TCA
It is important to understand that the review of TARN data by Barnard et al (2017a) showed that of the 705 patients in TCA who had complete data submitted between 2009 and 2015, 85% had a blunt trauma mechanism of injury. There were no statistically significant survival differences in the penetrating and blunt trauma groups. In addition, the highest surviving sub-group was of those who had an ROSC in the pre-hospital setting following blunt trauma.
Examining outcomes
There were 86.8% of patients with a severe traumatic brain injury (TBI) and/or a severe haemorrhagic injury; with 38.2% having both. Patients with a combination of these injuries had a lower chance of survival than those with only haemorrhagic injury or TBI. In the current review, patients with the best outcome were those who had suffered a TBI in isolation; 15.2% of this patient group survived to discharge, with 90% having good neurological outcomes (Barnard et al, 2017a).
In patients who had not suffered a TBI or severe haemorrhagic injury, the most prevalent aetiology was spinal injury, followed by thoracic injuries. Survival in these sub-groups were higher than overall (12.9% vs. 7.5%). Lockey et al (2006) performed a retrospective review on patients who had suffered TCA over a 10-year period, and reported that those with the highest survival are those who had a hypoxic insult (44% of 68 survivors). Those who have a thoracotomy following penetrating trunk trauma have also displayed improved outcome in various studies and systematic reviews (Narvestad et al, 2016). Importantly, Lockey et al (2006) found survival following hypovolaemic TCA to be very low, with only one survivor.
When HOT isn't so hot
Incidentally, 16% of 68 survivors were deemed to have had a primary medical event leading to the trauma. This is replicated in other studies and many authors recognise the difficulty in differentiating between medical and traumatic cardiac arrest. In these medical patients, it is vitally important to perform chest compressions, as recommended by a large evidence base (European Resuscitation Council, 2015). Adopting the HOT approach in these patients therefore may not be the optimal management plan.
HOT resuscitation
Lockey et al (2013), who developed the HOT algorithm, recommend that patients in TCA should have basic life support and chest compressions started. They state that patients in TCA may still benefit from the blood flow provided from chest compressions, but recognise that in hypovolaemia, they may be futile. This is reciprocated in the European Resuscitation Council (2015) Guidelines. Despite this, however, there has been an alarming anecdotal trend of clinicians suggesting they do not believe there is a role for chest compressions in TCA. The European Resuscitation Council (2015) state:
‘Chest compressions provide some blood flow during cardiac arrest and should be continued whilst the history and mechanism of injury have been accurately established.
‘In profound hypovolaemia, chest compressions are likely to be minimally effective due to poor cardiac filling and external compressions of an empty heart.’
They go on to state that:
‘immediate diagnosis of hypovolaemia can be difficult and, if in doubt, chest compressions should be continued.
‘The patients with the best chance of survival are normovolaemic and chest compressions can be at least partially effective whilst reversible causes are addressed simultaneously.’
Once reversible causes have been addressed, it is imperative to perform chest compressions to begin the blood flow in order to allow the interventions performed to take effect.
Theory of impact brain apnoea
There is increasing research on the theory of impact brain apnoea (Wilson et al, 2016). This refers to a pathology following a TBI whereby a patient may have a prolonged period of apnoea, eventually leading to cardiac arrest. Wilson et al (2016) refers to the cessation of breathing following a TBI, which is commonly precipitated by a large catecholamine surge, which presents initially as hypertension and then cardiovascular collapse. Clearly, in these patients, chest compressions may provide a benefit to restore blood flow. It is theorised that patients who have an impact brain apnoea can have positive outcomes if apnoea and hypoxia is reversed in a timely manner.
Hypovolaemia and chest compressions
In the civilian setting, in true and established hypovolaemia leading to cardiac arrest, survival is reported to be very low (Lockey et al, 2006). Outcome following resuscitation of hypovolaemic TCA may be improved in the setting of enhanced care, in the hospital and in the military setting. This may be attributed to damage control surgery and massive transfusion protocols, which cannot currently be replicated to civilian ambulance service care. The military adopt an approach of treating hypovolaemia with a massive transfusion protocol including blood products. It is important to note that the military are almost always treating hypovolaemic cardiac arrest, which is not replicated in the civilian setting (Barnard et al, 2017b). In addition, the vast majority of civilian responses to TCA do not have the capability for massive blood product transfusion.
Watts et al (2017) performed an animal study comparing ROSC and survival in hypovolaemia with various treatment measures (closed chest compressions (CCC)) vs. saline vs. CCC and saline vs. whole blood (WB) vs. WB and CCC) (Figure 1). Their method was inducing hypovolaemic TCA in monitored and terminally anaesthetised large swine. Watts et al (2017) concluded that CCC were associated with increased mortality compared with intravenous fluid resuscitation. Resuscitation with WB demonstrated the greatest physiological benefit as demonstrated by the highest numbers of animals achieving ROSC. This study supports the theory that it may be better to perform fluid resuscitation and not chest compressions when managing TCA if there are not sufficient resources to perform both simultaneously. In this study, however, the population had hypovolaemia as the only mechanism of arrest, which is not representative of the population of TCA treated by NHS ambulance services. Furthermore, owing to the immediate commencement of treatment following deterioration of mean arterial pressure, the pigs will likely have been in a ‘low-flow’ state, whereby the heart is still beating, but is unable to produce a pulse, as there is not enough volume. Unless the arrest is witnessed by the attending clinicians, it is unlikely that the patient will present in a low-flow state, and chest compressions may be required to facilitate blood flow and achieve ROSC.
Of note is that in the pre-hospital setting, usually ‘at the side of the road’, intravenous (IV)/intraosseous (IO) access can be time-consuming; studies have reported average time-to-insertion of between 2 and 5 minutes (Carr et al, 2008; Engels et al, 2014). It is often more challenging in hypovolaemia patients as a result of them being peripherally shut down. This represents a significant period of time without any chest compressions.
Therefore, in the civilian setting, without the use of blood products, where established hypovolaemia has significantly low survival, with some patients having aetiology which may benefit from chest compressions, it is difficult to recommend from the evidence performing fluid therapy as a priority over chest compressions in all cases of TCA.
Oxygenation
Intubation as a paramedic skill is a widely debated issue, following concern about success rates, lack of training, supervised practice and frequency of insertion (College of Paramedics, 2017). Intubation is widely accepted to bring more challenges than the insertion of a supra-glottic airway (SGA) (Taylor et al, 2016). Intubation is recommended to be a two-person intervention (one person assisting). In the initial management of TCA, there are multiple actions that need to be taken simultaneously.
It could be recommended that an SGA is inserted as the first airway adjunct in TCA. It can be rapidly inserted by an individual, and this can then be changed to an endotracheal tube at a later point in the resuscitation (if required) when other reversible causes have been addressed.
As discussed, those with the highest survival are those who have a hypoxic insult (Lockey et al, 2006). Once hypoxia has been addressed, it is essential to perform chest compressions to begin the blood flow, in order to allow the blood to be oxygenated in the hopes of achieving ROSC (European Resuscitation Council, 2015)
Tension pneumothorax
Patients in TCA may have a tension pneumothorax as a primary cause of their collapse (Huber-Wagner et al, 2007; Peters et al, 2017). Needle decompression is a skill that can be performed by NHS paramedics. The procedure can often fail owing to the needle not reaching the pleural space because of the thickness of the chest wall (Laan et al, 2016).
Despite this, it is simple and rapid to perform and may be able to provide temporary reversal of a tension pneumothorax, so should be recommended as a priority in TCA. The procedure should be performed on both sides of the chest, as assessing and identifying the signs and symptoms of significant chest trauma such as tension pneumothorax can be difficult. Various studies have concluded that the sensitivity and specificity of identifying significant chest pathologies with auscultation is relatively low (Chen et al, 2001; Kong et al, 2015; Ramsingh et al, 2016).
HOT in paramedic practice
Although providing guidance and support in a difficult subject HOT may not encompass optimal treatment for all patients who have suffered TCA. Furthermore, it must be acknowledged that care delivered in the military, hospital and enhanced care team settings differ from that delivered by NHS ambulance services. Without access to thoracostomies and blood products, it is unlikely that tension pneumothorax and hypovolaemia can be truly reversed.
TCA is a rare event for NHS ambulance service responders. It makes up an extremely low proportion of their overall work load, and to expect a complex, detailed understanding of the epidemiology, pathology and treatment regimes of TCA is onerous. It is imperative to provide simple, easy-to-follow guidelines which ‘do the most for the most’. NHS ambulance services can support their staff in handling these difficult cases by providing a laminated reference card for use while en route to the case. This may look like the one in Table 1.
| Control CAT haemorrhage and apply chest seals |
| Clear airway, insert SGA and ventilate |
| Perform bi-lateral needle decompression |
| Large volumes fluid replacement |
| Chest compressions |
| IF RESOURCES ARE LIMITED, PRIORITISE TREATING SUSPECTED CAUSE OF ARREST. |
|
Then Consider:
|
Adherence to best practice
In 2014, Yorkshire Air Ambulance Charity developed a treatment guideline for blunt TCA, similar to the one in Table 1 and introduced it into their service. They found that ‘all standards met’ improved from 5.9% to 40.7% (Mickwitz and Syrat, 2016). Mickwitz and Syrat (2016) reported ROSC on scene improvements from 17.6 to 37%; however, no patients were followed up post discharge.
This study, at minimum, shows that the introduction of a TCA guideline can improve adherence to what is currently thought to be best practice. A literature review by Chen et al (2016) on the introduction of checklists in pre-hospital emergency medicine demonstrated that safety, outcome and adherence to guidelines can be improved. Kerner et al (2017) also demonstrated improved adherence to treatment guidelines by the introduction of checklists and algorithms.
Conclusion
To conclude, the de-emphasis of chest compressions may not benefit the UK civilian population who suffer TCA. In addition, both Lockey et al (2013) and the European Resuscitation Council (2015) guidelines emphasise the benefits of chest compressions. The benefit of chest compressions is well supported in the evidence for cardiac arrests from medical causes (European Resuscitation Council, 2015); however, limited evidence is available for and against chest compressions in trauma.
Many patients who have suffered a TCA following aetiology such as TBI or neurogenic shock may benefit from chest compressions, and those who have had a medical event leading to trauma will certainly benefit from chest compressions.
The principle of early treatment of reversible causes in TCA is likely to improve outcomes. HOT is a memorable acronym and has significant momentum in guiding treatment in the management of TCA. However, HOT should not be misquoted as advocating no chest compressions, as this could lead to ineffective treatment of a group of patients who may otherwise have had favourable outcomes. First resources on scene should concentrate on control of haemorrhage, managing the airway rapidly by insertion of an SGA, chest decompression and beginning chest compressions.
Other interventions may be more appropriately performed when further resources have arrived on scene. Where clinicians strongly suspect hypovolaemia as the primary cause of arrest, it may be appropriate to gain vascular access and begin volume replacement prior to chest compressions if there are insufficient resources to perform both simultaneously.